The present invention is directed toward heat exchangers, and particularly toward vehicle heat exchangers having flat tubes with deformed ends.
Heat exchangers having fins between flat tubes, which tubes are deformed at their ends for connection to headers, are well known in the art.
In some such heat exchangers, the tubes have their ends flared outwardly enabling adjacent tubes to be connected to one another at the ends notwithstanding the fins between the tubes across the length of the tubes. However, particularly when the heat exchanger is used as a radiator for cooling engine coolant, the small diameter of the flat tubes is relatively limited, often in the range of less than 2 mm. In such cases, particularly where the flaring is formed by a cut along the sides of the flat tube, the resulting surfaces along the sides of the tube ends are so small that they can result in unsatisfactory solder (brazed) connections to the sides of the headers or tanks to which they are connected.
DE 195 43 986 A1 shows a structure in which the tube ends are flared together with a header secured to the front and back sides of the tube ends. It is apparent from FIGS. 4 and 6 of DE 195 43 986 A1 that the depth or width of the deformed ends of the flat tubes is reduced to the extent that the headers are much narrower than the fin and flat tube heat exchange core. If the tube width were not as sharply reduced, problems with respect to soldering connections would also increasingly occur there. The spacing between the flat tubes and the height of the fins arranged between them would also necessarily be further reduced, which would cause the tube-header or tube tank connections to undesirably constrain the design parameters used for such critical heat exchange components.
Further, especially when the depth of the fin and flat tube heat exchange core must be limited due to space constraints, for example, in the range from 20 to 30 mm, the headers or tanks may also be undesirably narrowed even further, which can lead to undesirable high pressure loss in the coolant.
The present invention is directed toward overcoming one or more of the problems set forth above.
In one aspect of the present invention, a heat exchanger is provided including a heat exchanger core having a plurality of flat tubes with fins between adjacent tubes, the tubes each having flat side walls connected by front and rear walls defining a flow path, all of the walls extending longitudinally between opposite tube ends with the tube side walls defining a first height. First tube end portions in the tube ends of a plurality of the plurality of flat tubes include flat side walls flared apart to define a second height greater than the first height. Second tube end portions in the tube ends of the plurality of the plurality of flat tubes include a longitudinally extending cut through the front and rear walls with the flat side walls flared apart to define a third height greater than the second height. The side walls of adjacent tubes are secured together at the tube ends, and headers or tanks connect to the tube front and rear walls at the first and second tube end portions whereby the headers or tanks communicate with the tube flow paths.
In one form of this invention, a longitudinally extending portion of at least one of the side walls is connected to the side wall at an end of an adjacent tube.
In another form of this invention, the first tube end portions are produced by a compression and flaring process.
In still another form of this aspect of the invention, the second tube end portions are produced by at least one separation cut and the bending of least one of the side walls of the plurality of the plurality of flat tubes. In this form, the longitudinally extending cuts in the second tube end portions may terminate before the first tube end portions.
In still other forms of this invention, the second tube end portion is symmetric relative to the flat tube or is asymmetric relative to the flat tube.
In yet another form of this aspect of the invention, the longitudinally extending cuts of the second tube end portions are substantially centered between the longitudinally extending tube side walls.
In still other forms, the side walls of adjacent tubes are secured together at the tube ends by solder, and/or the headers are connected to the tube front and rear walls by solder.
In another aspect of the present invention, a heat exchanger such as described is produced with the second tube end portions formed by flaring apart the tube side walls, with the headers secured to the first tube end portions prior to the flaring apart of the tube side walls to form the second tube end portions.
In still another aspect of the present invention, the heat exchanger as described is produced by flaring apart the first and second tube end portions to define a second height greater than the first height, with the front and rear walls of the second tube end portions thereafter longitudinally cut.
In yet another aspect of the present invention, the heat exchanger as described is produced with the first tube end portions being defined by flaring the side walls apart and compressing the front and rear walls together.
According to another aspect of the present invention, the heat exchanger as described is produced with the front and rear walls compressed together an amount substantially the same as the thickness of the tank walls secured thereto, whereby the depth of the core is substantially equal to the depth of the headers.